Biodiesel is the name for a variety of ester-based oxygenated fuels made from vegetable oils, fats, greases, or other sources of triglycerides. Biodiesel is a nontoxic and biodegradable blendstock which may be blended with petroleum diesel provided relevant specifications are met. Blends of biodiesel with petroleum diesel can reportedly substantially reduce the emission levels and toxicity of diesel exhaust. Biodiesel has been designated as an alternative fuel by the United States Department of Energy and the United States Department of Transportation, and is registered with the United States Environmental Protection Agency as a fuel and fuel additive.
Because biodiesel is made from numerous different feedstocks (e.g. rapeseed oil and palm oil), including mixed feedstocks, a finished fuel manufacturer is often not aware of the exact feedstock composition of a purchased biodiesel. Biodiesel is commonly referred to by its feedstock source (e.g. rapeseed methyl ester, palm oil methyl ester). Since the performance of a biodiesel depends upon the particular feedstock mixture from Which it was produced, formulators are therefore often unable to predict how the biodiesel will perform in the finished fuel blend. In the case of blends containing two or more biodiesels, it can prove difficult to anticipate whether the blend will afford a performance advantage such as an improved cetane number, or will in fact suffer from a performance disadvantage (such as poor low-temperature operability) that might call for the addition of a performance enhancer.
PCT WO2005028597 discloses fuel blends that contain mixtures of fatty acid methyl esters derived from different sources such as rapeseed methyl ester, palm oil methyl ester.
Sarin, et al., “Jatropha-Palm biodiesel blends: An optimum mix for Asia”, Fuel 86 (2007) 1365-1371, discloses blends of jatropha and palm biodiesels that have low temperature and oxidative stability properties that are well-suited to use in Asia.
Park, et al., “blending effects of biodiesels on oxidation stability and is low temperature flow properties”, Bioresource Technology 99 (2008) 1196-1203, predicts the oxidation stability and cold filter plugging point of blends of palm, rapeseed, and soybean biodiesels.
Moser, “Influence of Blending Canola, Palm, Soybean, and Sunflower Oil Methyl Esters on fuel Properties of Biodiesel”, Energy & Fuels 2008, 22, 4301-4306, discloses fuel properties of single, binary, ternary, and quaternary blends of canola, palm, soybean, and sunflower oil methyl esters.
While the above references reflect efforts to identify the operating properties of biodiesel blends, the need continues to exist for fuels and blending strategies that will yield improved combinations of petroleum distillates and fatty acid alkyl ester-containing biofuels.